The invention relates to a device for soundproofing motion picture cameras.
Motion picture cameras have motor and gear devices for the continuous transport of a motion picture film between a film cassette and the motion picture camera, for the intermittent transport of the motion picture film along an image window in which the motion picture film is exposed, and for a rotating diaphragm device with the aid of which the beam path from the recording objective to the image window is interrupted during the film transport. These motor and gear devices produce mechanical vibrations that reach the camera housing as air-borne and structure-borne noise, and are radiated there to the environment, thus causing interfering or unacceptable ambient noises during sound film recordings. In order to minimize the self-noise level of a motion picture camera, it is therefore necessary to prevent the transmission of these unavoidable vibrations to the outer skin of the motion picture camera.
For the purpose of soundproofing or the suppression of sound, insulating materials such as rubber and the like are inserted between the movable parts of the film recording camera and the camera housing, but they have the disadvantage of a low mechanical stability, and so there is a need for frequent readjustment, since the camera objective determining the focal point plane is fastened on the camera housing, while the image window that determines the image plane for exposure of the motion picture film is part of the movable parts of the motion picture camera, and so every variation in the clearance between the camera housing and the camera frame carrying the movable parts of the motion picture camera causes instances of image blurring and/or image shifts.
U.S. Pat. No. 4,174,157 A discloses a motion picture camera having a camera housing that has an objective fastening, and a camera frame that is arranged inside the camera housing and on and in which the movable parts of the motion picture camera that produce noise are arranged. Provided between the camera frame and the camera housing are connecting elements that absorb sound and have an externally threaded pin that can be screwed into the camera housing and/or into the camera frame and is held by an internally threaded socket between which and an externally threaded bearing bush, a hollow cylindrical elastomer insert is provided.
The externally threaded pin, the internally threaded socket, the elastomer insert and the externally threaded bearing bush are arranged coaxially with one another, and the externally threaded bearing bush is held by an internally threaded element on the respective other part of the camera housing or of the internal camera. If the externally threaded bearing bush is rotated inside the internally threaded socket after the loosening of the externally threaded pin, the internal camera and the movable camera parts can be aligned laterally with reference to the camera housing, and thus to the objective fastening.
This known device for soundproofing the internal camera and/or the camera frame from the camera housing requires constant readjustment at the sound absorbing connecting elements in order to ensure observance of the support dimension between the objective holder on the camera housing and the image plane on the camera frame.
DE 40 28 540 C2 discloses a device for soundproofing motion picture cameras having a soundproofing support of the camera frame carrying the noise-producing parts of the camera mechanism and the camera housing that has an objective carrier to which an exchangeable recording optics is fastened, and a number of sound insulating connecting elements are arranged between the camera frame and the camera housing for the purpose of the soundproofing support of the camera frame in the camera housing. In order, on the one hand, to observe the support dimension without readjustment and, on the other hand, to ensure optimum soundproofing, the sound insulating connecting elements have a directionally dependent inherent rigidity with a high, firmly defined and temperature-compensated rigidity in the direction of the support dimension between the objective plane of the camera housing and the image plane of the camera frame, as well as a low rigidity in the plane perpendicular thereto.